The present invention relates first to a method of operating an internal combustion engine, in which exhaust gas flows out from at least one combustion chamber after termination of a working stroke via at least one outlet valve driven by an actuator, in which a pressure value is determined, which is indicative of the gas pressure in the combustion chamber during the working stroke.
The invention also relates to a computer program, an electrical storage medium for an electronic control unit of an internal combustion engine, and an electronic control unit used for operating an internal combustion engine.
A method of the above-described type is known from the market. With this method, the gas pressure prevailing during a working stroke in a combustion chamber is directly detected by a sensor, for example, a piezo sensor. Alternatively, it is also known to estimate a mean gas pressure in a combustion chamber during a working stroke and/or during a complete operating cycle based on a measurement and evaluation of the asymmetry of the oscillating rotational speed of a crank shaft. Information about the gas pressure in the combustion chamber during a working cycle can be used to determine the corresponding amount of torque generated by the combustion and/or to estimate the position of the center of heat release during combustion relative to the rotating crank shaft. In addition, the quality of the combustion (for example, incomplete combustion, misfire, and so on) can be evaluated based on the knowledge of the gas pressure in the combustion chamber. All this information can be exploited to achieve an operation of the combustion engine with minimal fuel consumption, minimal noxious exhaust emissions, and an optimal running smoothness.
Therefore, an object of the present invention is to provide a new method of the above-described type, which enhances operation of the internal combustion engine with respect to the above-mentioned quality factors like, for example, running smoothness, while simultaneously preserving or enhancing cost-effectiveness of its manufacturing process.
This object is solved for an internal combustion engine equipped with an outlet valve with variable opening stroke by a method of the above-described type, in which an actual opening stroke or lift of the outlet valve is determined together with actual values of the operating parameters of the internal combustion engine affecting this opening stroke, and in which, based on the determined actual lift of the outlet valve and the determined actual operating parameters of the internal combustion engine, an actual gas pressure in the combustion chamber at the time of the opening of the outlet valve is calculated at least approximately.